Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

A method for operating a mechatronic chassis device of a motor vehicle,
wherein the mechatronic chassis device has an arrangement with two
servomotors which, when activated, individually change both a toe angle
(δ) of a wheel and a camber angle (ε) of the wheel. The
servomotors are controlled on the basis of target values in a
predetermined manner, wherein if a first servomotor cannot be placed into
operation, an emergency program is started and the second servomotor is
controlled in a manner different from the predetermined manner such that
a lateral force on the wheel is adjusted to a predetermined desired
value.

Claims:

1-8. (canceled)

9. A method for operating a mechatronic chassis device of a motor vehicle
having a first arrangement with two first servomotors, each of the two
first servomotors individually changing upon activation both a toe angle
of a first wheel and a camber angle of the first wheel, comprising the
steps of: controlling the two first servomotors in a predetermined manner
based on target values for the toe angle and the camber angle, starting
an emergency program when a first of the two first servomotors cannot be
placed in operation, and controlling the second of the two first
servomotors with the emergency program in a manner different from the
predetermined manner, such that a lateral force on the first wheel is
adjusted to a predetermined desired value.

10. The method of claim 9, wherein the predetermined desired value
depends on a steering angle set on a steering handle.

11. The method of claim 9, wherein the predetermined desired value
corresponds to a minimum value of the lateral force.

12. The method of claim 9, wherein the emergency program allows value
combinations for toe angles and camber angles in addition to the target
values.

13. The method of claim 9, wherein the mechatronic chassis device
comprises a second arrangement for a second wheel with two second
servomotors, each of the two second servomotors of the second arrangement
individually changing upon activation both a toe angle of a second wheel
and a camber angle of the second wheel, wherein the two second
servomotors of the second arrangement are also controlled in a
predetermined manner based on target values, wherein in the emergency
program, at least one of the two second servomotors of the second
arrangement is also controlled in the manner different from the
predetermined manner.

14. The method of claim 13, wherein the first and second wheels are
disposed on opposite sides of the motor vehicle.

15. The method of claim 9, comprising the steps of: coupling a wheel-side
support element of a wheel carrier, which supports a motor vehicle wheel
for rotation, and an axle-side support element of the wheel carrier by
way of an actuator having a wheel-side rotary member and an axle-side
rotary member, and rotating one of the wheel-side rotary member and the
axle-side rotary member relative to the other axle-side rotary member or
wheel-side rotary member with a servomotor associated with the one rotary
member about a rotation axis associated with the one rotary member.

16. A mechatronic chassis device comprising: a wheel carrier which
comprises a wheel-side support element supporting a vehicle wheel for
rotation and an axle-side support element, an actuator coupling the
wheel-side support element and the axle-side support element together,
wherein the actuator comprises a wheel-side rotary member and an
axle-side rotary member, a servomotor associated with each of the
axle-side rotary member and the wheel-side rotary member for rotating the
axle-side rotary member and the wheel-side rotary member about
corresponding rotation axes, and control devices configured to control
the servomotors in a predetermined manner based on target values for a
toe angle and a camber angle, start an emergency program when a first of
the servomotors cannot be placed in operation, and control a second of
the servomotors with the emergency program in a manner different from the
predetermined manner, such that a lateral force on the vehicle wheel is
adjusted to a predetermined desired value.

Description:

[0001] The invention relates to a method for operating a mechatronic
chassis device of a motor vehicle according to the preamble of claim 1.

[0002] It is assumed that a mechatronic suspension device which allows
setting a toe angle of a wheel and a camber angle of the same wheel
includes two servomotors. However, each of these servomotors are
configured as part of an associated device to not only set one of the
angles; instead, each servomotor alone should, when activated,
simultaneously change the toe angle of the wheel and the camber angle of
the wheel.

[0003] A chassis device with the aforementioned properties is disclosed,
for example, in WO 2009/052914 A1. The chassis device described therein
allows setting the toe angle and camber angle in a particularly simple
manner without introducing undue mechanical complexity. The wheel
suspension for motor vehicles from WO 2009/052914 A1 is illustrated in
the FIGS. 1 and 2 of the present application. The wheel carrier 3 has a
wheel-side supporting member 17 on which a vehicle wheel 1 is rotatably
mounted. The wheel carrier further includes an axle-side supporting
element 19. The two support elements 17 and 19 are interconnected by an
actuator 21. This interconnected actuator 21 includes a wheel-side rotary
member 23, which is connected to the supporting element 17 and an
axle-side rotary member 25, which is connected to the support element 19.
Each rotary member 23, 25 is able to rotate about an axis 27, 28 (FIG.
2). The rotation takes place with the aid of servomotors 38 and 39. When
rotating by a rotation angle α, the rotary member 23 moves with a
tumbling motion about the rotation axis 27. Simultaneously or with a time
offset, the rotary member 25 can be rotated by a rotation angle β
relative to the support element 19. When rotating the two rotary members
23, 25, the wheel-side rotary member 23 is deflected by a pivot angle
φ relative to the axle-side rotary member 25. A desired toe angle
δ and a desired camber angle ε of the wheel 1 can be set by
suitably adjusting the rotation angles α and β of the
respective rotary members 23, 25.

[0004] It will be assumed that the servomotors are controlled in a
predetermined manner, see the connections 51 for a control unit 53. The
control unit 53 processes target values relating to the toe angle δ
and the camber angle ε; to implement the target values, the
servomotors are then driven in a predetermined manner, as disclosed in WO
2009/052914 A1.

[0005] However, there is a risk that one of the servomotors cannot be
operated, either because it has an inherent failure, or because the
connection 51 to the control unit 53 is inoperative.

[0006] Since the failure of these components cannot be predicted or
controlled, it may happen that a certain toe angle and a certain camber
angle are set at a certain time of a failure, which should not to remain
permanently set. On the other hand, not every desired track angle in
combination with any desired camber angle can be set with the remaining
operative servomotor alone.

[0007] It is an object of the present invention to increase the
operational safety of a motor vehicle having a chassis device with the
aforementioned characteristics.

[0008] The object is attained with a method having the features of claim
1: Accordingly, when a first servomotor cannot be placed in operation, an
emergency program is started, and the second servomotor is driven in a
manner different from the predetermined manner.

[0009] In other words, the second servomotor is not simply turned off and
the accidentally adjusted toe angle and the accidentally adjusted camber
angle are not accepted as such. On the other hand, the second servomotor
is not operated as if the first servomotor were still functioning. The
emergency program can thus take into consideration that not all
combinations of toe angle--camber angle can be any longer freely
adjusted. It is thus possible to strive for a compromise.

[0010] It is hereby no longer entirely important that a desired toe angle
and a desired camber angle are precisely adjusted, i.e. that a target
setting is implemented in a predetermined manner. The focus is instead on
safety, which can be defined, for example, based on the lateral force
applied on the wheel. Preferably, the second servomotor is controlled in
the emergency program such that a lateral force on the wheel is adjusted
to have a predetermined target value.

[0011] The toe angle and the camber angle together affect the lateral
force. The lateral force is the force which forces the motor vehicle from
moving in a straight line into a turn. To create a particular driving
condition, a target value for the lateral force can be defined. To still
ensure safe steering, it is advantageous when the target value for the
lateral force depends on a steering angle set on the steering handle or
steering wheel of the motor vehicle: When driving through a curve, the
target value for the lateral force may be adjusted so that the desired
curve is traversed safely, whereas the lateral force can be adjusted to
be substantially zero when driving in a straight line.

[0012] In normal operation, the two servomotors may not always be able to
adjust all possible angles due to software-based limitations. In this
case, certain combinations of values for toe angles and camber angles may
be excluded. However, because various combinations of values may already
not be attainable as a result of the failure of a servomotor, at least
those combinations of values for toe angles and camber angles are then
preferably allowed in the emergency program (as additional value
combinations), which are otherwise excluded. This increases the
flexibility; for example, the lateral force can be more accurately
adjusted to a target value.

[0013] The inventive method can also be extended to include more than one
wheel. In particular, the arrangement with the two servomotors, which
simultaneously change the toe angle and the camber angle of a wheel, is
typically installed a second time on a side of the motor vehicle opposite
to the aforementioned wheel, i.e. once on the left side of the motor
vehicle and once on the right side of the motor vehicle. According to the
invention, if a servomotor of one of the arrangements fails, at least one
servomotor on the respective other arrangement disposed on the opposite
side of the motor vehicle is controlled by the emergency program in a
manner different from the usual manner. Through intervention on the
wheel, which is located on one side opposite the side on which the
servomotor is not operative, the motor vehicle can still have excellent
stability in spite of the failure of the first servomotor on the one side
of the motor vehicle.

[0014] The method is preferably used with the type of mechatronic chassis
device disclosed in WO 2009/052914 A1 and described above. Control
electronics may be provided; however, the detailed design of the control
electronics is not important in this context. Preferably, however, a
control unit is configured to execute the emergency program, if
necessary.

[0015] In one aspect, a mechatronic chassis device is provided, wherein
the control device allows execution of the emergency program.

[0016] Preferred embodiments of the invention will now be described with
reference to the drawings, in which

[0018]FIG. 2 shows in a more detail diagram the wheel carrier used in the
corresponding mechatronic chassis device of FIG. 1,

[0019]FIG. 3 shows a schematic diagram of the hierarchy of control units
in a motor vehicle, in which the present invention can be used, and

[0020]FIG. 4 shows a flow diagram for explaining an embodiment of the
inventive process.

[0021] The mechatronic chassis device of FIG. 1 is to be provided on both
wheels on an axle of a motor vehicle according to the invention. In FIG.
3, the respective servomotors 38 and 39 for the left side are designated
as M1 and M2 and for the right side as M3 and M4. Respective electronic
control units are associated with each of the servomotors M1 to M4, which
are also referred to as "Power Electronics" and which are therefore
abbreviated with the abbreviation LE1 to LE4. They correspond to the
connection 51 of FIG. 1. One control unit, which can also be referred to
as "Actuator Controller" and which corresponds to the control unit 53 of
FIG. 1, is associated as a master with each of two power electronics. The
actuator controller 1, labeled "AR1" in FIG. 3, is responsible for the
servomotors M1 and M2 on the left wheel, the actuator controller "AR2"
for the right side. A chassis controller FR (control unit) is
additionally associated with the two actuator controllers AR1 and AR2 as
a master.

[0022] The toe angle and camber angle to be set are determined in the
chassis controller. Each of the actuator controllers AR1 and AR2 then
determines which servomotor is to perform which rotation. Accordingly,
the actuator controllers AR1 and AR2 transmit commands to the power
electronics LE1 and LE2 and LE3 and LE4, respectively, which then apply
an electric current to the corresponding motors M1 and M2 or M3 and M4.
The inventive process is executed on the plane of the actuator
controllers AR1 and AR2 and runs on one of these controllers.

[0023] In principle, in one embodiment, the method can also be executed on
the plane of the chassis controller FR; however, this is not preferred.

[0024] According to FIG. 4, the inventive process begins at step S10, with
the first actual step indicating that the chassis controller FR generates
a new target setting for toe and camber which is received by an actuator
controller AR1, AR2. At step S14, the actuator controllers AR1 and AR2
then check whether a failure occurred in the subordinated units LE1, LE2
and ME1, ME2. (It is assumed here that only one error occurs at one
time.) As long as no error occurs, the target setting is implemented by
the actuator controller AR1 at step S16, as described above. At step S12,
a new desired setting is then generated, and an error check is again
performed at step S14. If at some point an error is found at step S14,
for example, because the motor M1 has failed or because the associated
power electronics LE1 has failed, or both, an emergency program is
started at step S18. The associated actuator controller AR1 then controls
the intact group composed of the power electronics LE2 and the motor M2,
however, in a different way than would be done at step S16: When
implementing the target setting, it is assumed that control commands can
be transmitted to both power electronics LE1 and LE2. In the present
case, however, control commands are only transmitted to the power
electronics LE2 for activating the motor M2, taking into account the
failure of the motor M1 and its associated power electronics LE1. In
particular, it will be ensured that a lateral force FS, which is
defined as being perpendicular to the motor vehicle's vertical axis Fha
and illustrated in FIG. 1, is controlled to a desired value or adjusted
to be as close as possible to the desired value. The chassis controller
FR now replaces the toe-camber combination previously set by the chassis
controller FR with a new target value for toe and camber, which produces
in the actual driving situation a value for the lateral force FS
that is as close as possible to the value for the lateral force defined
by the original toe-camber combination.

[0025] It is then checked at step S22, whether the quantities defining the
desired lateral force have changed. Such quantity may include, for
example, the steering angle set at a steering handle or steering wheel of
the motor vehicle: the greater the steering angle is, the greater is the
desired lateral force. Additional quantities defining the desired lateral
force are the speed or the rotation speed on the wheel 1.

[0026] After a change in the quantities defining the desired lateral
force, the process transitions again to step S20, and the new desired
lateral force is controlled.

[0027] The method of FIG. 4 ends when the failure has been repaired. To
encourage a motor vehicle owner to bring his motor vehicle in to be
repaired, a warning signal may be outputted, if necessary, in particular
simultaneously with the step S18.